This invention relates generally to pipeline strainers, and more particularly to strainers for medium and large diameter pipes which have a strainer or screen member which is removable for cleaning purposes.
Many industrial processes and equipment utilize pipeline systems for circulating water, steam, or other fluids for various purposes, and such systems may include various sensitive components such as regulators, steam traps, meters, pumps and other equipment that can easily be damaged by contaminants such as scale and other solid particles which can enter the system from a variety of sources. While many such systems do not require the complete freedom from contamination that is provided by special filtration equipment, it is usual to place strainer units at various places in the pipeline system for removing the larger size particles of contaminants. Such strainers may be used in various sized pipes from the smallest up to 36 inches or larger, and provide a housing in which is mounted a perforated screen element which may be formed either from woven mesh screen or from perforated sheet metal having openings sufficiently small in size to trap damaging particles and sufficiently large in number to prevent any substantial pressure drop through the strainer.
One common type of strainer is the so-called Y-type which has a body having an in-line inlet and outlet for mounting in a straight section of pipe. The housing has a branching portion extending at an acute angle with the outlet and mounting a cylindrical screen which is held in place by an outlet plug or cover which may have a reduced diameter blow-off plug therein. These strainers are mounted in a pipeline so that the fluid entering the inlet is deflected through an acute angle down the lower or strainer leg of the Y into the cylindrical strainer basket. The fluid then passes radially outward through openings in the side of the cylinder forming the screen, leaving any contaminant particles therein for removal by cleaning either by opening the blow-off opening or removal of the end cover. After the fluid has passed through the strainer, it must flow back upwardly to leave through the outlet in line with the inlet. Such strainers are widely used because they are relatively low cost to manufacture and can often be at least partially cleaned by mere removal of the blow-off plug. However, such strainers provide relatively limited screen area and require changes in direction of flow and increased turbulence in the fluid so that they tend to produce a relatively high pressure drop, particularly at high rates of flow.
Another type of pipeline strainer is the so-called basket strainer, which again has an inlet in line with the outlet and a wall separating the inlet and outlet that extends at an angle with respect to the axis, as from the bottom of the inlet to the top of the outlet. In this wall is located an opening to receive a cylindrical basket having a bottom end formed of screen material as well as the side walls, and having an oblique top having a flange adapted to mate with the opening in the wall. In such strainers, the fluid entering the inlet moves downwardly into the basket through the opening in the transverse wall, and then moves radially outward to the outlet opening. In strainers of this type, the area of the basket can be substantially greater than in strainers of the Y-type, and there is less turbulence and restriction to flow because of the more direct flow path between the inlet and the outlet. Such strainers usually have a cover above the basket held in place by bolts, or a clamp, for quick removal, so that cleaning can be accomplished by removing the cover and pulling out the basket, which usually has an attached handle in the form of a bail engaging the cover at the top to hold the strainer basket in place in the opening in the transverse wall. While such strainers have the advantage of increased filter area, easy cleaning, and low pressure drop, they tend to be rather large and bulky in size and more expensive than the Y-type for equal straining capacity.